Display technologies have included television cathode ray tubes, plasma displays, and various forms of flat panel displays. Typical television cathode ray tube displays utilize an emissive coating, typically referred to as a “phosphor” on an interior, front surface, which is energized from a scanning electron beam, generally in a pattern referred to as a raster scan. Such television displays have a large, very deep form factor, making them unsuitable for many purposes.
Other displays frequently used for television, such as plasma displays, while having a comparatively flat form factor, involve a complex array of plasma cells containing a selected gas or gas mixture. Using row and column addressing to select a picture element (or pixel), as these cells are energized, the contained gas is ionized and emits ultraviolet radiation, causing the pixel or subpixel containing a corresponding color phosphor to emit light. Involving myriad gas-containing and phosphor-lined cells, these displays are complicated and expensive to manufacture, also making them unsuitable for many purposes.
Other newer display technologies, such as active and passive matrix liquid crystal displays (“LCDs”), also include such pixel addressability, namely, the capability of individually addressing a selected picture element. Such displays include a complex array of layers of transistors, LCDs, vertically polarizing filters, and horizontally polarizing filters. In such displays, there is often a light source which is always powered on and emitting light, with the light actually transmitted controlled by addressing particular LCDs within an LCD matrix. Such addressing, however, is accomplished through additional layers of transistors, which control the on and off state of a given LCD.
Currently, creation of such displays requires semiconductor fabrication techniques to create the controlling transistors, among other things. A wide variety of technologies are involved to fabricate the liquid crystal layer and various polarizing layers. LCD displays also are complicated and expensive to manufacture and, again, unsuitable for many purposes.
Using simpler fabrication techniques, electroluminescent lamp (EL) technology has provided for printing or coating emissive material, such as phosphors, in conjunction with conductive layers, to form signage and other fixed displays. For these displays, a given area is energized, and that entire area becomes emissive, providing the display lighting. Such prior art EL displays, however, do not provide any form of pixel addressability and, as a consequence, are incapable of correspondingly displaying dynamically changing information. For example, such prior art EL displays cannot display an unlimited amount of information, such as any web page which may be downloaded over the internet, or any page of a book or magazine, also for example.
Such prior art displays which are incapable of pixel addressability include those discussed in Murasko U.S. Pat. No. 6,203,391, issued Mar. 20, 2001, entitled “Electroluminescent Sign”; Murasko U.S. Pat. No. 6,424,088, issued Jul. 23, 2002, entitled “Electroluminescent Sign”; Murasko U.S. Pat. No. 6,811,895, issued Nov. 2, 2004, entitled “Illuminated Display System and Process”; and Barnardo et al. U.S. Pat. No. 6,777,884, issued Aug. 17, 2004, entitled “Electroluminescent Devices”. In these displays, electrodes and emissive material are printed or coated on a substrate, in a “sandwich” of layers, in various designs or patterns. Once energized, the design or pattern is illuminated in its entirety, forming the display of fixed, unchanging information, such as for illuminated signage.
These prior art static electroluminescent displays are subject to various problems which severely limit their utility and other practical uses. For example, such prior art static electroluminescent displays are not scalable to form factors larger than a typical sheet of A4 or 8½ by 11 inch paper; in particular, the various transmissive conductive material utilized do not conduct sufficiently rapidly to illuminate larger areas, failing to energize the central portions of larger displays and thereby failing to provide corresponding illumination. In addition, such prior art static electroluminescent displays are typically designed to form a backlighting of an independently created image. For example, such prior art static electroluminescent displays require separate and independent image application, such as through image transfer of a pre-printed four color image, or independent positioning of a separate translucent sheet containing the image to be illuminated, such as separate signage printed on a clear material and overlaid upon the prior art static electroluminescent displays. Such prior art static electroluminescent displays also incapable of being fully integrated with a printed design to form an integrated display having both artwork and electroluminescent regions, particularly for detailed artwork printed at high resolution (using non-screen printing techniques), largely due to very significant variations in the surface topology of the finished displays.
Prior art static electroluminescent displays also require manufacture using multiple and very different technologies. For example, many such displays require sputtering technologies and separate lamination of various layers forming the electroluminescent lamp.
In addition, such prior art static electroluminescent displays have significant durability limitations, resulting in comparatively short usable lifetimes. For example, under typical environmental conditions having some humidity, the prior art static electroluminescent displays are subject to failure and other loss of performance. Such prior art static electroluminescent displays are also subject to significant issues of short circuits, also causing a fault condition.
As a consequence, a need remains for a scalable electroluminescent display, which may provide substantially larger form factors, suitable for applications such as outdoor signage. In addition, such an electroluminescent display should provide a printable surface, for direct application of an image to be illuminated. Such an electroluminescent display should provide for an optically or visually neutral density surface, for underlying layers to have negligible perceived visual effect. Such an electroluminescent display should also provide for significant durability with a capability to withstand typical environmental conditions, especially for outdoor applications or other applications in environments having variable conditions.
Such prior art displays also do not provide for a dynamic display of changing information, particularly for information which was not preprinted and fixed during manufacture. As a consequence, a further need remains for a dynamic emissive display which provides for pixel addressability, for the display of dynamically changing information. Such a display further should be capable of fabrication using printing or coating technologies, rather than using complicated and expensive semiconductor fabrication techniques. Such a display should be capable of fabrication in a spectrum of sizes, from a size comparable to a mobile telephone display, to that of a billboard display (or larger). Such a display should also be robust and capable of operating under a wide variety of conditions.